Book Image

Mastering Reactive JavaScript

By : Erich de Souza Oliveira
Book Image

Mastering Reactive JavaScript

By: Erich de Souza Oliveira

Overview of this book

If you’re struggling to handle a large amount of data and don’t know how to improve your code readability, then reactive programming is the right solution for you. It lets you describe how your code behaves when changes happen and makes it easier to deal with real-time data. This book will teach you what reactive programming is, and how you can use it to write better applications. The book starts with the basics of reactive programming, what Reactive Extensions is, and how can you use it in JavaScript along with some reactive code using Bacon. Next, you’ll discover what an Observable and an Observer are and when to use them.You'll also find out how you can query data through operators, and how to use schedulers to react to changes. Moving on, you’ll explore the RxJs API, be introduced to the problem of data traffic (backpressure), and see how you can mitigate it. You’ll also learn about other important operators that can help improve your code readability, and you’ll see how to use transducers to compose operators. At the end of the book, you’ll get hands-on experience of using RxJs, and will create a real-time web chat using RxJs on the client and server, providing you with the complete package to master RxJs.
Table of Contents (11 chapters)

Acting when an error occurs

When an error occurs, the observable stops sending new data. We can use different strategies, such as switching to another observable or retry, but these are more advanced so first we will see how an observer can be notified by an error. As you probably remember, the subscribe() method from the observable object lets you pass up to three functions or allows an observer to be notified when an error occurs.

Take a look at the following signature:

observable.subscribe([onNext], [onError], [onCompleted]); 

The parameters are optional:

  • onNext: This function is to be called when new data is available in this observable. The function receives the data itself as a parameter.
  • onError: This function is to be called when an error is propagated through this observable. This function received the Error as a parameter.
  • onCompleted: This function is to be called when the observable is exhausted and all the data has already been propagated.

This method also has an overloaded implementation...